text: # -*- coding: UTF-8 -*-
  """
  Software: LingFeat - Comprehensive Linguistic Features for Readability Assessment
  Page: EnDF.py (Entity Density Features)
  License: CC-BY-SA 4.0
  
  Original Author: Bruce W. Lee (이웅성) @brucewlee
  Affiliation 1: LXPER AI, Seoul, South Korea
  Affiliation 2: University of Pennsylvania, PA, USA
  Contributing Author: -
  Affiliation : -
  
  References:
  >>> Entity Density features inspired by 
  Publication 1: Feng, Lijun, Noémie Elhadad, and Matt Huenerfauth. "Cognitively motivated features for readability assessment." Proceedings of the 12th Conference of the European Chapter of the ACL (EACL 2009). 2009.
  """
  
  def retrieve(NLP_doc, n_sent, n_token):
          to_EntiM_C = 0
          to_UEnti_C = 0
          ent_list = []
          unique_ent_list = []
  
          for ent in NLP_doc.ents:
              to_EntiM_C += 1
              ent_list.append(ent.text)
          
          for ent in ent_list:
              if ent_list.count(ent) == 1:
                  to_UEnti_C += 1
                  unique_ent_list.append(ent)
  
          result = {
              "to_EntiM_C": to_EntiM_C, 
              "as_EntiM_C": to_EntiM_C/n_sent, 
              "at_EntiM_C": to_EntiM_C/n_token,
              "to_UEnti_C": to_UEnti_C, 
              "as_UEnti_C": to_UEnti_C/n_sent,
              "at_UEnti_C": to_UEnti_C/n_token,
          }
  
          return result